Derrick



(No Model.)

0. CROSBY.

DERRICK. No. 388,839. Patented Sept. 4, 1888.

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OLIVER CROSBY, OF ST. PAUL, MINNESOTA.

DERRICK.

SPECIFICATION forming part of Letters Patent No. 388,839, dated September 4, 1888.

(No model.)

1'0 all whom it may concern:

Be it known that LOLIvER Ouoscv, a citizen of the United States, residing in the city of St. Paul, county of Ramsey, State of Minnesota, have invented a new and useful Improvement in Dcrricks, ofwhich the following is a specification.

My invention relates to improvements in derricks; and it consists in a step-plate and derrick-foot so constructed as to allow ropes to pass through the same, and which are free to revolve relatively to each other, but secured together so as not to be separated by a lifting force on the derriekniast.

The invention is illustrated in the accompanying drawings, in which Figure l is a side elevation of a derrick, partly in section, showing my improvements, 'a portion of the mast and rope passing down the same being broken away. Fig. 2 is a frontview of the derrick foot and step; Fig. 3,a top view of the (lerriclefoot; Fig. 4,an err larged perspective view of the gih used for locking the derrick bottom and step.

Similar letters designate corresponding parts in each figure.

In the drawings, A represents the mast,and

B the derrick-foot casting, partially inclosing i the bottom of the mast and having a shelf plate or bracket, a,upon one side, upon which the weight of the mast and the downward strain upon the same are supported. This casting has two wings, I) b, which serve to support the boom G by means of the pivot c, passing through the same and the lower end otthe boom. The said pivot 0 also serves as a bearing for the sheave D, running loosely thereon in a slot formed in the end of the boom.

E E are straps for the further support of the boom 0.

F is the step upon which the derrick is supported, having a trunnion, (7,, projecting upwardly therefrom, and upon which, as a pivot, the derrick is mounted and turns by means of a circular aperture, 6, formed in the bottom of the foot 13, closely fitting the trunnion. The trunnion projects somewhat above the upper surface of the base of the foot B, and around its circumference is formed a groove, f, the under side of said groove being flush with the upper surface of the said base-plate. Keys or gibs G G, passing through suitable slots, 9 g, in the sides of the foot 13, resting upon the base-plate and entering said groove upon the opposite sides of the trunnion, hold the foot B in place upon the same and prevent the derrick from jumping out of place by reason of any lifting strain upon the same. The gibs g g are bent up at right angles outside of the slots in the sides of the foot-casting, and the turned-up portion is bolted to the foot, as shown at h 7z,to prevent them from becoming disengaged from the grooves in the trunnion. The step F has an aperture, 2', extendingentirely through the same in thecenter of the trunnion d for the passage of ropes from the top of the derrick.

Upon the under side of the step-plate, and just forward of the edge of the aperture t, are two downwardly-extending wings or armsflc it, between which are mounted two or more sheaves, H H,over which pass the ropes from the top of the derrick and from the boom 0, the said sheaves H, H, and D being so located that the line of the aperture 1 shall be substantially tangential thereto in a vertical direction.

At the top of the mast is the cap I, having an aperture in its top to receive the gudgeon Z, and upon the side of this cap toward the direction of the boom are cast two wings forming hangers for one or more sheaves m. Upon the ends of the pivot upon which the sheaves m, are carried is attached a stirrup, n, for at taching the end of the line, which extends thence over a sheave connected with the outer end of the boom, over sheave m, and thence downward around sheave H to the motive power.

I claim as my invention- The combination, with the foot B, having bearings adapted to support the mast and boom of a. derrick, and having an aperture in the bottom thereof, of a trunnion extending through and fitting within said aperture and havinga circumferential groove formed therein above the plane of said bottom, and gibs attached to said foot and entering said groove, substantially as and for the purpose herein specified.

OLIVER CROSBY.

Witnesses:

H. S. Wool), F. J. JOHNSON. 

